title: Dipyridamole-related enhancement of gap junction coupling in the GM-7373 aortic endothelial cells correlates with an increase in the amount of connexin 43 mRNA and protein as well as gap junction plaques.
abstract: Previous data showed that dipyridamole enhanced gap junction coupling in vascular endothelial and smooth muscle cell lines by a cAMP-dependent mechanism. The present study investigates the level at which dipyridamole affects gap junction coupling. In the GM-7373 endothelial cell line, scrape loading/dye transfer experiments revealed a rapid increase in gap junction coupling induced during the first 6 h of dipyridamole treatment, followed by a slow increase induced by further incubation. Immunostaining analyses showed that the rapid enhancement of gap junction coupling correlated with an increased amount of Cx43 gap junction plaques and a reduced amount of Cx43 containing vesicles, while the amount of Cx43 mRNA or protein was not changed during this period, as found by semiquantitative RT-PCR and Western blot. Additionally, brefeldin A did not block this short-term-induced enhancement of gap junction coupling. Along with the dipyridamole-induced long-term enhancement of gap junction coupling, the amount of Cx43 mRNA and protein additionally to the amount of Cx43 gap junction plaques were increased. Furthermore, the anti-Cx43 antibody detected only two bands at 42 kDa and 44 kDa in control cells and cells treated with dipyridamole for 6 h, while long-term dipyridamole-treated cells showed a third band at 46 kDa. We propose that a dipyridamole-induced cAMP synthesis increased gap junction coupling in the GM-7373 endothelial cell line at different levels: the short-term effect is related to already oligomerised connexins beyond the Golgi apparatus and the long-term effect involves new expression and synthesis as well as posttranslational modification of Cx43.
authors.affiliation: Institute of Biophysics, Leibniz University Hannover, Herrenhäuserstr. 2, D-30419 Hannover, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Begandt
authors.forename: Almke
authors.initials: A
authors.lastname: Bader
authors.forename: Linda
authors.initials: L
authors.lastname: Gerhard
authors.forename: Julia
authors.initials: J
authors.lastname: Lindner
authors.forename: Lutz
authors.initials: L
authors.lastname: Dreyer
authors.forename: Barbara
authors.initials: B
authors.lastname: Schlingmann
authors.forename: Anaclet
authors.initials: A
authors.lastname: Ngezahayo
mesh_terms: D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D004176:Dipyridamole / Q000494:pharmacology*; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*
chemical_list: D018031:Connexin 43; D012333:RNA, Messenger; D004176:Dipyridamole